In insulating jugs sealing between the stopper and the housing of the jug is generally effected by exerting pressure on the sealing element. In the case of insulating jugs with a recess at the top into which the stopper is inserted and from which a spout or a tube branches off to one side, the sealing element, comprising a sealing disc or sealing ring, is arranged on the underside of the stopper, and cooperates with the bottom of the recess surrounding the opening of the insulating jug.
In the case of known insulating jugs with a tubular spout it is already known to provide an additional seal between the top of the housing and a cover embracing the top of the housing, in order to prevent liquid from escaping between the stopper and the upper rim of the housing when the jug is in a steeply inclined pouring position.
Another construction is known in which a pouring channel is provided in the stopper that by-passes the seal and can be closed by a closure member by means of a mechanism that passes through the stopper.
Sealing problems can arise in the constructions described above, first if the sealing surface itself is not flat, and second if different initial and final positions of the seal or the sealing surface result from dimensional discrepancies, which may be additive, whereby the sealing is impaired. The problem arises from the manufacturing technique and depends on the material of the parts, and also occurs with insulating jugs made of plastic. Hitherto elastic, i.e. compressible, sealing elements have been provided to solve this problem. While these allow for compensation of tolerances, they have the disadvantage in terms of handling technique that compression of the sealing element requires the use of a substantial amount of force. In addition the relatively large amount of force used leads to increased wear, which reduces the life of the seal. The problems described above arise in particular in the case of insulating jugs with screw stoppers having set open and closed positions, for example indicated by marks. In one known construction the screw stopper has to be turned through 180.degree. between its open and closed positions so that in the open position the mark is on the side facing towards the spout and in the closed position it is on the opposite side. In the case of this construction this provides another cause of possible dimensional discrepancies.